//二叉树剪枝

class Solution {
public:
    TreeNode* pruneTree(TreeNode* root) {
        if(root == nullptr) return nullptr;
        root->left = pruneTree(root->left);
        root->right = pruneTree(root->right);
        if(root->left == nullptr && root->right == nullptr && root->val == 0)
        {
            root = nullptr;
        }
        return root;
    }
};